Heart diseases include acute coronary syndrome, atherothrombosis, restenosis, hypertension, stable angina, arrhythmia, cardiac failure, ST-segment elevation myocardial infarction, and the like. As a target substance in the treatment of these heart diseases, thrombin is contemplated which is one of blood coagulation factors. Receptors for GP (glycoprotein) IIb/IIIa (platelet membrane glycoproteins) can also be targets for treating heart diseases. Further, it is known that thrombin receptors are present in cells such as platelets, vascular smooth muscle cells, endothelial cells and fibroblast cells. Thrombin receptors can also be targets for treating heart diseases.